Microstructural characterization of martensite with long period stacking order structure in Hf-Co-Pd alloy

Microstructural characterization of martensite with long period stacking order (LPSO) structure in a Hf-Co-Pd alloy was investigated by transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). LPSO structure with six stacking sequences; 6O (orthorhombic) (Space group: Immm), were newly discovered. Based on the electron diffraction experiments, the lattice parameters of LPSO phase were estimated to be a = 0.33 nm, b = 0.45nm and c = 1.53 nm. The formation mechanism of martensite with LPSO structure and the crystallographic orientation relationship between parent B2 phase and 6O martensite are also discussed.